Brady admits he has secretly battled with depression for years and describes the harrowing emotions he's experienced. "People are like, 'Wayne Brady's always happy!'" he says. "No I'm not. Because I'm human."

"Having a bad day is one thing, having a bad week is another, having a bad life … You don't want to move, you can't move in the darkness," he explains. "You're like, 'I am just going to sit right here and I want to wallow in this. As much as it hurts, I am going to sit right here because this is what I deserve. This is what I deserve, so I am going to sit here because I am that horrible of a person.'"

"It starts this cycle where you tell yourself these lies ... and those lies become true to you," he says. "So, you stick to your own truth you've set up. 'If I am this bad, then why should any of this matter?' I feel at that point, you end up wanting to stop the pain."

Brady reveals he hit rock bottom last June on his 42nd birthday, recalling, "I was there by myself, in my bedroom and I had a complete breakdown … Just go ahead and imagine for yourself a brother in his underwear, in his room, you got snot … and that birthday was the beginning of, 'OK, I've got to make a change.'"

Brady, who knew Williams from the comedian's appearance on Whose Line, tweeted on the day news broke of Williams' death.

"When he was on stage [in] full-on Robin mode -- and I know this from being blessed enough to work with him -- you could not touch that man," he tells ET. "He made all these people feel great. And at the same time, knowing that he had this sense of … what I make up in my mind, this low sense of self-worth, of belonging, of loneliness, of pain that all the money in the world can't cure, all the accolades and awards, and all the love from people all over the world … all that love could still not stop that man from saying, I am in so much pain.'"

He also points out the double standard in Hollywood when it comes to admitting to depression as opposed to a drug problem.

"Nobody wants to out themselves so to speak, or if they out themselves, it's in a very -- I hate to say it -- Hollywood way," he says. "It's actually cool to go into rehab for some people. ... But if someone says, 'I'm clinically depressed,' that sounds like someone's making something up. It's like, ‘Psst, you're not depressed.'"

Brady now says he's currently on the road to recovery, and gives a lot of credit to his ex-wife, Mandie Taketa. He says the two are still close friends, despite divorcing in 2007 after eight years of marriage. They remain committed to co-parenting their daughter Maile, now 11.

"We said we want to give her the closest experience she can have to living in the same house," he says of being neighbors with his ex. "And we've always lived in different homes. We just live super-close now. The fact of the matter is, I like her mom. She was down with me when nobody in the world was down with me, except my mom. There was loyalty there, there was respect, there is trust -- she is my baby mama."

He also has this piece of advice for those battling with their own struggles with depression.

"It took me a while to get my stuff together to go, 'You know what? If you're not happy, you have to do something about it,'" he says frankly. "Just to admit that you are feeling this way is a huge step. To claim that, to say, 'Why do I feel dark? Why do I feel unhappy? Let me do something about this.'"